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Signals Better At Night Than Day?

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btritch

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Curiosity Question, Is it actually true that Radio Signals from Scanner transmissions such as PD/FD/ETC. travel further at night than at day due to the atmosphere and ionoshpere? I've always heard they do but didn't know if it was actually true...Anyone ever researched this?
 

n5usr

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The ionosphere won't affect VHF/UHF frequencies, that's the domain of HF. However, there is tropospheric ducting that can cause VHF/UHF to carry for hundreds of miles under the right conditions. This is related to weather, many times VHF propagation will go nuts as a storm front moves in.

Wikipedia has a page on it:
http://en.wikipedia.org/wiki/Tropospheric_ducting#Tropospheric_ducting

Now, there is less atmospheric noise at night, so stations that were making it just as far during the day but were below the noise floor may be above the noise floor - and thus audible - at night.

HF is where you more regularly see the day/night effect. As the sun goes down, the Maximum Usable Frequency (MUF) goes down. The higher bands (above the MUF) will "go dead" since the ionosphere won't bounce those frequencies and any signals just radiate out into space. The lower bands will "go long" - the distance between bounces back down to the earth grows longer.

There's a lot more to it than that, but it gives you the highlights! :p
 

Smerri

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I always notice I pull in further communities (and clearer) at night.

Don't know the facts or science behind it, but it is definately true in my case.
 
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lugoffman

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Smerri said:
I always notice I pull in firther communities (and clearer) at night.

Don't know the facts or science behind it, but it is definately true in my case.
i get things more clearer at night to it is weard though
 

Zaratsu

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generally the lower the freq, the bigger the night/day difference will be. There are exceptions of course to this rule, but in general scanner frequencies, this is usually the case. And I mean whole different bands. 50-54mhz will have a bigger change than 460mhz will at night. Generally a whole "band" will play by the same rules from my understanding.
 

zz0468

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It really depends on the local weather and geographic conditions. But yes, in general, things can change at night and it can significantly alter how signals propagate. Things that affect VHF/UHF propagation include temperature, humidity, pressure, the presence or lack of storm fronts, and so on. Basically, if it affects the weather, it can affect radio signals.
 
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